The present invention relates to a wick type space heater mainly used for indoor heating and, more particularly, to a space heater having a wide heating power adjustment range.
Wick type space heaters have prevailed as indoor heating equipment. Conventional wick type space heaters are classified into wick slide type, fuel head type and fuel compression type heaters with respect to fuel supply systems. These types of heaters are further classified into single or plural cylinder type heaters.
The main part of a conventional wick type space heater, e.g., a typical plural cylinder type heater in a kerosene stove has the following construction. The main part comprises a fuel tank, inner and outer flame cylinders concentrically arranged above the fuel tank so as to constitute a combustion chamber therebetween, a narrow path for causing the combustion chamber to communicate with the fuel tank, and a wick, the lower end portion of which is dipped in kerosene in the fuel tank and the upper end portion of which is inserted in the combustion chamber through the narrow path to soak up kerosene by capillary action. A plurality of vent holes are formed in the inner and outer cylinders to supply air to the combustion chamber. The kerosene vapor evaporated from the upper end of the wick is combusted in the combustion chamber. In addition, by adjusting an exposed portion of the wick in the combustion chamber, the heating power is adjusted.
In such a kerosene stove, the upper end portion of the wick exposed in the combustion chamber is fired by an ignition unit, and air required for combustion is supplied from the plurality of vent holes formed in the inner and outer flame cylinders, thereby accelerating combustion. Heat generated by this combustion heats the exposed upper end portion of the wick in the combustion chamber to increase the evaporation amount of the kerosene. For this reason, the combustion area is gradually increased. In order to improve the combustion efficiency in a wick type kerosene stove, a combustion region is provided at the upper portion of the combustion chamber, and a premixing region for air and the fuel vapor must be provided at the lower portion of the combustion chamber. For this reason, the vent holes formed in the upper portions of the inner and outer flame cylinders generally have a larger diameter than those in the lower portions thereof, thereby limiting the amount of air supplied to the lower portion of the combustion chamber. As described above, when the combustion area is enlarged, it is gradually shifted from the lower portion to the upper portion of the combustion chamber. When the combustion region is shifted to the upper portion of the combustion chamber, heat received by the upper end portion of the wick reaches its upper limit, as does the evaporation amount of kerosene. As a result, when the heat radiated from the upper end portion of the wick is balanced with the heat supplied to the upper end portion thereof, a steady combustion state is achieved
In such a wick type kerosene stove, the following problem is presented. When the wick is moved downward to decrease the heating power, i.e., when the exposed portion of the wick exposed in the combustion chamber is decreased, the evaporation amount of kerosene is temporarily decreased to lower the heating power. However, the combustion region is shifted to a lower portion of the combustion chamber to increase the temperature of the upper end portion of the wick again, thereby increasing the evaporation amount of kerosene. Even if the wick is vertically moved to adjust the heating power, the actual adjustable range is very narrow. In addition to this disadvantage, smooth heating power adjustment cannot be performed. When the wick is rapidly moved upward to increase the heating power, i.e., when the exposed portion of the wick is rapidly increased, the upper end portion of the wick which is saturated with fuel is exposed in a high-temperature atmosphere. As a result, kerosene evaporation is rapidly accelerated, and complete combustion cannot be performed in the combustion chamber. Excessive flame rise leads to an unsafe condition. When weak combustion is set, the exposed portion of the wick must be sufficiently decreased. Under this condition, the combustion region is shifted to the lowermost position of the combustion chamber. As a result, the premixing region for air and fuel vapor is decreased to increase exhaustion of toxic gases such as CO and THC.